1. Field of the Invention
The present invention relates to a state monitoring apparatus for an assembled battery, the state monitoring apparatus including a high-voltage side monitoring section disposed in a high voltage system having an assembled battery constituted of a series connection of a plurality of battery cells to monitor the state of the assembled battery, and a low-voltage side monitoring section disposed in a low voltage system insulated from the high voltage system to monitor the state of the assembled battery through communication with the high-voltage side monitoring section.
2. Description of Related Art
It is known to provide a vehicle on which an electric motor is mounted as a vehicle main engine with an assembled battery constituted of a series connection of a plurality of battery cells as a high voltage battery to supply power to the motor. However, it may occur that remaining capacities of the battery cells differ from one another due to temperature variation among the battery cells and individual variation among the battery cells, causing variation in remaining capacity among the battery cells and accordingly voltage variation among the battery cells. When lithium batteries are used as the battery cells, if their remaining capacities increase excessively, that is, if the battery cells are overcharged, they are caused to deteriorate quickly. Accordingly, in this case, it is desirable to monitor the voltages of the battery cells.
Incidentally, since the high voltage battery is included in the high voltage system of a vehicle isolated from the low voltage system of the vehicle, it is necessary to transmit detection results by a voltage measuring means provided in the high voltage system to the low voltage system to monitor the state of the assembled battery on the side of the low voltage system. However, there is a problem that data amount and the time needed to transmit the detection results increase as the number of the battery cells constituting the high voltage battery increases.
To cope with this problem, there is proposed a technique in which when a battery voltage measuring device is activated, the measured voltages of all the battery cells are transmitted to the low voltage system, then the battery cells whose voltages are respectively at the maximum and minimum of all the battery cells are identified on the side of the low voltage system, and thereafter, the measured voltages of only the identified batteries are transmitted to the low voltage system at appropriate timings. For example, refer to Japanese Patent Application Laid-Open No. 2002-42906.
However, in the above technique, since most of the battery cells are not measured except the time of activation of the battery voltage measuring device, it is not possible to monitor the state of the high voltage battery sufficiently and reliably.